A simple way is creating a profile (Plot->profile), select the item to create(e.g. xdisp ) and draw a line along the top surface, and then create a profile, in the profile window, right click on the plot, press ‘view data’, you can output the values with x and y coordinates as *.CSV file. You can also use command directly to export the data to a file, the syntax is shown below:
How can you export “zone list profile disp-x …“ to csv in FLAC2D 9.6 ?
i think there is no direct command, probably you should create a list of values, and then write a text file with that information using a fish/python function